The present invention relates to arc welding systems in general and, more particularly, to an arc welding system with image acquisition.
Recent developments in the robotics industry have highlighted the need for accurate vision systems not only for parts identification, but also for robot guidance. U.S. Pat. No. 4,105,925, is an example of an optical object locator which determines the position and orientation of parts on a moving conveyor through the use of two planes of light that intersect at a single transverse line on the conveyor circuit. The two planes of light are located at an acute angle with respect to the conveyor. A linear diode array is aligned with the single line of light on the conveyor. When a part or other object on the conveyor moves through the line of light, it intercepts the light above the coneyor at positions spaced laterally from the line of light. The linear diode array senses only the line segments on the conveyor located beyond the object or part boundaries. Through the use of electronic sampling of the illumination on linear array, the object or part boundaries are determined and the part shape and orientation are thereby detected.
Automated arc-welding or seam welding is a recent and expanding addition to the manufacturing process, particularly in the automotive industry. Although the quality and consistency of the finished weld is high, difficulties inherent in the process have to be addressed in the design of a robotic system. Arc-welding is often one of the last in a series of manufacturing steps, each of which may contribute tolerance errors to piece parts. Furthermore, the welding process itself introduces thermal stresses and deformations in the weldment. Typically, the repeated presentation of parts to be welded is accomplished by fixturing or tooling which fixes in space the components to be joined. The accuracy of this positioning will influence the final tolerance of the weldment.
A skilled human welder will adapt his welding to accomodate the vagaries of weldment seam position and fit-up. However, there exists few effective mechanisms in automated welding to accomplish these ends. It is estimated that at least thirty percent of the welding tasks otherwise appropriate for robot welding do not meet the minimum criteria for accuracy in dimensionality, part fit-up or fixture positioning.
In order to achieve the maximum benefits from robotic arc welding, the welding apparatus should be able to determine the geometry and location of the weld seam in the presence of the welding arc by mens of a suitable vision sensor. Given this information, adjustments then can be made to position accurately the welding torch and thus, accomodate inaccuracies in the weldment.
It is accordingly, a general object of the present invention to provide an arc welding system with image acquisition.
It is a specific object of the invention to provide an arc welding system with image acquisition which utilizes a non-planar beam of light to illuminate a portion of the welding object which portion is thereafter imaged on a detector to produce corresponding signals representative of the image thereon.
It is another specific object of the invention to provide an arc welding system with image acquisition in which the non-planar beam of electro-magnetic radiation takes the form of a hollow conical beam of light that is generated by means of a concave, cylindrical reflector.
It is still another object of the invention that the image acquisition apparatus is used in conjunction with a plural axis manipulator to provide guidance and identification information for controlling the welding torch.
It is a further object of the invention to provide an arc welding system with image acquisition in which the image acquisition apparatus is optically and physically shielded from the arc of the welding torch.
It is a feature of the invention that the image acquisition apparatus shield is easily replaceable and at a very modest cost.
It is another feature of the invention that the method thereof can be practiced with relatively conventional electro-optical components.